1. Field of the Invention
This invention relates to Drive Train Fluids (DTF's) which include automatic transmission fluids (AFT's), manual transmission fluids, gear and axle lubricants, comprising oil-soluble transition metal compounds with the exception of zinc compounds. Various oil-soluble transition metal compounds have been discovered to ameliorate low temperature thickening in, e.g., automatic transmission fluids and high temperature thickening and the formation of insolubles in fluids such as gear lubricants. The oil-soluble transition metal compounds may be formulated in relatively low concentrations with the particular Drive Train fluid to achieve the desired effect.
2. State of the Art
Since 1949 when General Motors developed the first fluid specifically for use in automatic transmisions, automatic transmission fluids have become accepted for use in a wide variety of applications. These include not only automatic transmissions of commercial vehicles and city buses, but also for power steering pumps, manual gear boxes, power shift transmissions and hydraulic equipment including vane and piston pumps. These various applications as well as the specifications and property requirements for such automatic transmission fluids is discussed in a paper presented by R. Graham and W. R. Oviatt titled "Automatic Transmission Fluids--Developments Toward Rationalization" at the CEC 1985 International Symposium, June 7, 1985, Wolfsberg, Germany.
Like automatic transmission fluids, gear and axle lubricants have a wide application in automotive equipment. Because of this wide use of automotive gear lubricants for numerous applications, the gear lubricants, as well as axle lubricants, in use today must be formulated to have a wide range of properties and meet a variety of specifications. Such requirements and specifications for gear lubricants are discussed, for example, in a paper by L. F. Schiemann et al titled "Impact of Vehicle Changes Upon Gear Lubricant Requirements," SAE paper No. 831732 presented at the SAE Fuels and Lubricants Meeting, San Francisco, Calif., Nov., 1983.
Additives have been widely used in automatic transmission fluids for improving the properties of these fluids, for example, in U.S. Pat. No. 4,532,062 various amine or ammonium salts of mercaptobenzothiazole are disclosed as additives which are useful as corrosion inhibitors, antioxidants and friction modifiers for automatic transmission fluids.
Various transition metal compounds have been employed in lubricating oils, specifically crankcase oils to improve the properties of these oils. For example, in U.S. Pat. No. 4,397,749, various oil-insoluble metal thiolates are combined with alkenyl or alkylmono- or bissuccinimides to render the metal thiolates oil-soluble, and these complexes are then formulated with lubricating oils as effective antioxidants and antiwear agents.
Likewise, in U.S. Pat. No.4,466,901, various molybdenum-containing compounds are added to lubricating oils as friction modifying agents. In U.S. Pat. No. 4,552,677, copper salts of succinic anhydride derivatives are added to lubricating oils, particularly crankcase lubricating oils to act as antioxidant agents and friction modifying agents.
In European Patent Application No. 24,146, lubricating oils, specifically crankcase oils, are disclosed containing a low concentration of oil-soluble copper compounds as an antioxidant.
None of the foregoing disclosures disclose or suggest the use of transition metal compounds in automatic transmission fluids or gear lubricants, particularly in the concentration range of the present invention and for the particular purpose of the present invention.